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. 2024 Mar 15;28(1):82.
doi: 10.1186/s13054-024-04867-6.

Effects of prone positioning on lung mechanical power components in patients with acute respiratory distress syndrome: a physiologic study

Christoph Boesing  1 , Joerg Krebs  2 , Alice Marguerite Conrad  2 , Matthias Otto  2 , Grietje Beck  2 , Manfred Thiel  2 , Patricia R M Rocco  3 , Thomas Luecke  2 , Laura Schaefer  2
Affiliations

Effects of prone positioning on lung mechanical power components in patients with acute respiratory distress syndrome: a physiologic study

Christoph Boesing et al. Crit Care. .

Abstract

Background: Prone positioning (PP) homogenizes ventilation distribution and may limit ventilator-induced lung injury (VILI) in patients with moderate to severe acute respiratory distress syndrome (ARDS). The static and dynamic components of ventilation that may cause VILI have been aggregated in mechanical power, considered a unifying driver of VILI. PP may affect mechanical power components differently due to changes in respiratory mechanics; however, the effects of PP on lung mechanical power components are unclear. This study aimed to compare the following parameters during supine positioning (SP) and PP: lung total elastic power and its components (elastic static power and elastic dynamic power) and these variables normalized to end-expiratory lung volume (EELV).

Methods: This prospective physiologic study included 55 patients with moderate to severe ARDS. Lung total elastic power and its static and dynamic components were compared during SP and PP using an esophageal pressure-guided ventilation strategy. In SP, the esophageal pressure-guided ventilation strategy was further compared with an oxygenation-guided ventilation strategy defined as baseline SP. The primary endpoint was the effect of PP on lung total elastic power non-normalized and normalized to EELV. Secondary endpoints were the effects of PP and ventilation strategies on lung elastic static and dynamic power components non-normalized and normalized to EELV, respiratory mechanics, gas exchange, and hemodynamic parameters.

Results: Lung total elastic power (median [interquartile range]) was lower during PP compared with SP (6.7 [4.9-10.6] versus 11.0 [6.6-14.8] J/min; P < 0.001) non-normalized and normalized to EELV (3.2 [2.1-5.0] versus 5.3 [3.3-7.5] J/min/L; P < 0.001). Comparing PP with SP, transpulmonary pressures and EELV did not significantly differ despite lower positive end-expiratory pressure and plateau airway pressure, thereby reducing non-normalized and normalized lung elastic static power in PP. PP improved gas exchange, cardiac output, and increased oxygen delivery compared with SP.

Conclusions: In patients with moderate to severe ARDS, PP reduced lung total elastic and elastic static power compared with SP regardless of EELV normalization because comparable transpulmonary pressures and EELV were achieved at lower airway pressures. This resulted in improved gas exchange, hemodynamics, and oxygen delivery.

Trial registration: German Clinical Trials Register (DRKS00017449). Registered June 27, 2019. https://drks.de/search/en/trial/DRKS00017449.

Keywords: Acute respiratory distress syndrome; End-expiratory lung volume; Lung-protective ventilation; Mechanical power; Prone positioning; Respiratory mechanics; Ventilator-induced lung injury.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
A Schematic workflow of the study. B Mechanical power components during volume-controlled ventilation with constant inspiratory flow. Area A (white) describes the resistive power component. Areas B and C describe the elastic dynamic and elastic static power components, respectively; together they are the total elastic power (teal). PpeakRS, airway peak pressure; PplatRS, airway plateau pressure
Fig. 2
Fig. 2
Effects of supine and prone positioning on A lung total elastic power and B lung total elastic power normalized to end-expiratory lung volume (EELV). A ventilation strategy with positive end-expiratory pressure (PEEP) based on the PEEP/FiO2 table during supine positioning was used as the baseline. A ventilation strategy with esophageal pressure-guided PEEP was used for the comparison between supine and prone positioning. Boxplots show the interquartile range and median with whiskers according to Tukey's method. Outliers are shown as circles. Brackets denote statistically significant differences between positioning and ventilation strategies; P values are shown above the brackets
Fig. 3
Fig. 3
Effects of supine and prone positioning on A lung elastic static power and B lung elastic static power normalized to end-expiratory lung volume (EELV). A ventilation strategy with positive end-expiratory pressure (PEEP) based on the PEEP/FiO2 table during supine positioning was used as the baseline. A ventilation strategy with esophageal pressure-guided PEEP was used for the comparison between supine and prone positioning. Boxplots show the interquartile range and median with whiskers according to Tukey's method. Outliers are shown as circles. Brackets denote statistically significant differences between positioning and ventilation strategies; P values are shown above the brackets
Fig. 4
Fig. 4
Effects of supine and prone positioning on A lung elastic dynamic power and B lung elastic dynamic power normalized to end-expiratory lung volume (EELV). A ventilation strategy with positive end-expiratory pressure (PEEP) based on the PEEP/FiO2 table during supine positioning was used as the baseline. A ventilation strategy with esophageal pressure-guided PEEP was used for the comparison between supine and prone positioning. Boxplots show the interquartile range and median with whiskers according to Tukey's method. Outliers are shown as circles. Brackets denote statistically significant differences between positioning and ventilation strategies; P values are shown above the brackets
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